Many wells produce substantial volumes of oil mixed with some water and sand. Sand flows from the formation with the fluids into the well. A typical pumping well normally includes a tubing string which is perforated at the lower end to admit fluid from the producing formation into the tubing string. The fluid flow from the formation carries with it some of the sand. As the fluid level in the well rises to submerge the pump, the pump is able to operate. Moreover, the stirring and agitatation of the pump tends to keep sand suspended in the liquid. Thus, the pump will lift a substantial quantity of sand.
Some wells are able to be pumped continuously. Others must be shut down periodically. In both cases, the pump lifts a column of liquid which stands from the pump to the well head. As the column is lifted, the sand in it tends to settle out. Depending on the viscosity of the recovered fluids, the size of the sand particles and their quantity, they tend to settle back and fall to the bottom of the tubing string. When this occurs, the pump itself will be sanded up on the exterior.
A pump is normally installed by fitting it against an inwardly protruding shoulder, and a seal is perfected below the shoulder by incorporating a set of encircling seal rings on the pump. If a significant quantity of sand settles on the pump, it makes it impossible to pull the pump. The pump then is locked in its position by the sand particles which settle around it.
The present invention is an apparatus which relieves this problem. It is an apparatus to be incorporated with pre-existing pumps or newly manufactured pumps. It is a modification to pre-existing pumps in that it is able to be installed at least in certain models of pre-existent pump to relieve sand locking in the well.
It has been discovered that the sand collects at a location typically just above the inwardly protruding shoulder where the pump is supported at the desired elevation. The present invention is a pair of telescoping tubular members which are installed in that pump. The exterior wall of the pump in ordinary circumstances is thus unmodified, namely, it remains an elongate tubular structure. The present invention thus incorporates a pair of telescoped tubular members which are joined together by a shear pin. As long as the axial load on the pump during retrieval is less than the anticipated load, indicating that the pump is not sand locked, then the tool is readily retrieved and the present invention is not required to operate to relieve the sand lock of the pump. It is only when pump is sand locked that the present invention comes into play. It incorporates a pair of tubular sleeves which are telescoped together. The outermost tubular sleeve is threaded to the lower end of the pump. The interior tubular sleeve is threadedly joined to the upper portions of the pump. The two are shear pin joined in the retracted condition. It is only when resistence is encountered that the present invention comes into play. If the pump is sanded and therefore locked in the tubing string, a suitable upward pull breaks the shear pin which joins the telescoped tubular members. The internal tubular member has a surrounding protruding lip at the lower end which is sufficiently large to lock it against pulling through the outer tubular member. When the shear pin is broken, the inner tubular member slides upwardly and positions a set of slots which open to the interior adjacent to the sand. The sand is then washed through the slots and down through the center of the tool and out through the bottom of the pump which is hollow. The invention works quite well even if the sand extends many feet above the pump. It should be kept in mind that the column of liquid standing above the pump is able to wash down past the pump and into the slots carrying great quantities of sand with it.